背景技术：
[0002]Various embodiments described herein relate to light sources, particularly luminaires, for providing special lighting patterns. These embodiments have particular, but not exclusive, usefulness in providing what is known in the art as “batwing” lighting patterns.
[0003]In many illumination systems, targeted areas to be illuminated are much larger than an emitting area of the light sources. Many artificial light sources emit light in an approximately Lambertian distribution. When illuminated from above by such a source, flat targeted areas such as roads, floors, or a work surface cannot be illuminated uniformly without modifying the intensity distribution of the light source. When a light source with Lambertian intensity distribution illuminates a flat surface from above, the intensity on that surface will be greatest directly under the light source, and will decrease monotonically for points on the surface farther away. A “batwing” distribution, conversely, reduces the intensity at nadir (directly under the light source) and increases the intensity at angles up to some maximum angle, such that the surface is illuminated substantially uniformly for angles less than the maximum angle. Batwing radiation patterns or light distributions can exist in several forms: one-dimensional (1D) batwings have a batwing shape only to the sides (e.g. East-West direction) and are often used with linear lighting. Two-dimensional (2D) circular batwing distributions create a batwing “cone” of light, illuminating evenly in all radial directions to achieve a disc-shaped area of uniform illumination on a flat surface. 2D square or rectangular batwings create a batwing “pyramid” of light, illuminating evenly in both North-South and East-West directions to achieve a square- or rectangular-shaped area of uniform illumination on a surface, substantially filling in dark corners between luminaires arrayed in a square or rectangular array on a ceiling. Frequently luminaires with batwing distributions can provide the desired uniformity of illumination at a greater luminaire-to-luminaire spacing than with Lambertian luminaires, meaning that fewer luminaires are necessary to illuminate the desired area, saving cost. In addition, the nadir suppression involved in a batwing distribution means minimum lighting levels can be met across the surface without far exceeding that minimum level at the nadir, which would unnecessarily waste energy.
[0004]A downward-facing light source with Lambertian light distribution has luminous intensity that is proportional to the cosine of the angle from nadir (the downward-facing direction). A Lambertian light distribution is represented in polar coordinates in FIG. 1. When a flat surface such as a floor is illuminated by a Lambertian light distribution, the illuminance on the floor is greatest at nadir (directly under the fixture) and decreases monotonically for points on the floor away from nadir. The central brightness is often referred to as a “hot spot” in the lighting industry, and is generally undesirable. By definition, the Full Width at Half Maximum (FWHM) of a Lambertian distribution is 120 degrees. In the lighting industry, the term “Lambertian” is also frequently used to refer to light distributions with similar quality but of different widths. That is, distributions that have a peak at nadir, and monotonically decrease at higher angles are often called Lambertian. In one example, a Gaussian distribution with FWHM of 80 degrees will often be called “Lambertian” in the lighting industry. Lambertian distributions are not batwing distributions.
[0005]For a single ceiling luminaire, which is small compared to the ceiling-to-floor distance, to uniformly illuminate a specified width across a flat surface such as a floor, it generally must emit light in a batwing distribution whose luminous intensity is inversely proportional to the cube of the cosine of the angle from nadir for angles less than the maximum angle. This theoretical distribution can be represented by the solid curve in FIG. 2, in which no light extends beyond the maximum angle. In practice, multiple luminaires are generally used to illuminate a surface such as a room, warehouse, or roadway, and it is desirable to have some overlap, or crossfade, between the light distributions emitted by each light source. Thus a practical batwing light distribution often has some light extending beyond the maximum angle, as illustrated in the dashed curve of FIG. 2. The sharp “peaks” of the light distribution in the solid curve are also disadvantageous because they can be noticeable to a viewer, and are hard to create in practice. The dashed curve of FIG. 2 shows more practical rounded peaks in the light distribution.
[0006]In practice, it is acceptable to have some level of variation of the illuminance on a surface. For various lighting applications, an illuminance variation of about 50%, 20%, 10%, 5%, or less may be acceptable across the surface of interest when illuminated by an array of luminaires. Because the specified level of variation allows for some deviation from ideal conditions, the batwing diffuser is allowed to have a light distribution that doesn't exactly follow the 1/cos3 distribution. This imperfection is illustrated in central portion of the dashed curve in FIG. 2.
[0007]Real-world lighting situations often include extra light, reflected from floors, ceilings, and/or other objects in the illuminated space. These reflections may be random in nature, and thus may increase the uniformity on the flat surface beyond the uniformity provided by the array of luminaires alone. This may also allow the luminaire's light distribution to deviate further from the ideal 1/cos3 distribution and still achieve a desired level of uniformity on the flat surface.
[0008]In lighting, batwing light distributions different from the typical inverse cosine cubed shape are also used. These may be desired, for example, in a library or store, in which it may be desired to illuminate vertical surfaces of shelves holding books or items. For these and other lighting applications, a degree of nadir suppression may be desirable that is greater or less than the typical inverse cosine cubed shape.
[0009]Other non-Lambertian lighting distributions are also beneficial for specific applications in lighting. Wall-grazer and wall-wash distributions seek to evenly illuminate a wall from a lighting fixture placed above and some distance from the wall. Narrow, collimated, or spot distributions seek to confine light in a narrow angular spread to provide very localized illumination. Asymmetric distributions may provide more light to one side of a fixture than the other side, for example to evenly illuminate a floor from a wall-mounted fixture.
[0010]Some lighting distributions seek to reduce glare, or light emitted at high angles, usually in the range of 65-90 degrees from nadir. Such light can reflect from computer monitors and reduce visibility. For office environments in the United States, ANSI/IESNA RP-1-04 suggests limits on light emission into these angles.
[0011]High-efficiency LED lighting is being increasingly adopted. Typical LED light sources emit light into a Lambertian distribution with a Full Width Half Max (FWHM) of approximately 120 degrees. Although LEDs with many other light distributions are available, many cost-effective LEDs sold for general lighting are of the 120 degree Lambertian variety. In many luminaires, a simple planar diffuser (such as a microstructured, holographic, or volumetric diffuser) is used to diffuse the LEDs, hiding their appearance from viewers and smoothing the surface appearance of the luminaire. These diffusers may not produce batwing distributions. Rather, they typically give Lambertian distributions of various widths (most typically about 80 to 120 degrees).
[0012]Conventional diffusers known in the art come in many varieties including volumetric, microstructured, holographic, and kinoform diffusers. Conventional diffusers can range in their diffusion strength from very light (in which an object viewed through the diffuser may be blurred but recognizable to very heavy (in which the diffuser may appear milky white and translucent, and objects may not be recognizable when viewed through the diffuser). The strength of the diffuser is sometimes characterized by illuminating one surface of the diffuser with a collimated light source such as a laser from a direction normal to the diffuser's surface, and goniometrically measuring the light output from the opposite surface. The diffuser is then defined by the Full Width at Half Maximum (FWHM) of the angular spread of light emitted from said opposite surface. Thus a 30-degree conventional diffuser when illuminated by a laser will produce a diffuse beam with substantially 30 degree FWHM. Conventional diffusers often have a symmetric, having the FWHM in all azimuthal orientations, while some diffusers may have an elliptical light distribution pattern, having one FWHM in a first azimuthal orientation, and a substantially different FWHM in a second azimuthal orientation substantially perpendicular to the first. Many other diffusion patterns are also known in the art.
具体实施方式：
[0106]For collimated light, beam shaping is well known in the art. Refractive and diffractive elements exist that can form a (collimated) laser beam into a specific shape. Such elements are available commercially, for example, from Jenoptik, Jena, Germany (http://wvvw.jenoptik.com/en-microoptics-refractive-optical-elements-ROEs). These elements can shape a laser beam into a line, crosshair, square, circle, and even images (such as corporate logos) to project on a surface, and are commonly used in machine-vision applications. Beam shapers generally require substantially collimated light, and generally have a planar (flat) form.
[0107]A prism cross-section, taken in the plane perpendicular to the substrate and perpendicular to the major orientation of the prisms is shown in FIG. 3A. The prism pitch 1 is the distance between successive prisms, and the prism internal angle 2 is the angle subtended by the peak of the prism in this cross-sectional plane. A prism film with prism internal angle 2 of 90 degrees is defined as a “90-degree prism” herein.
[0108]Prism films are used widely in the display industry (in the brightness-enhancing configuration, planar, with prisms facing away from the light source). Commercial prism films typically consist of 90-degree linear prisms formed of polymer on the surface of polymer films, often 50-250 microns in thickness. The prisms typically have a refractive index near 1.6, and a pitch ranging from 20-50 microns. They are available from a variety of manufacturers. One commercial example is BEF manufactured by 3M.
[0109]A 90-degree linear prism optic has one smooth surface and the other one is textured by an array of linear prisms with substantially 45-degree sidewalls, as shown in U.S. Pat. No. 3,288,990 and U.S. Pat. No. 4,542,449, in which one or two layers of prism optics are used to increase brightness directly under a luminaire, and reduce high-angle brightness. A film with the same properties is described in U.S. Pat. No. 4,906,070. A common application of such a prism optic is for brightness enhancement of the back light unit inside a display system, in which the prism optic is used flat over an extended, non-collimated light source, such as an array of LEDs, array of cold-cathode fluorescent lamps (CCFLs), or a side-illuminated light guide plate (LGP). In both lighting and display, a brightness-enhancing prism optic is used with the light entering smooth surface of the optic, and thus the prisms facing away from the light source. The prism optic is substantially planar or flat, with peak light emission substantially parallel to its surface. Rays incident perpendicular to the surface of the film will encounter total internal reflections (TIR) from the prisms. Those light rays are generally reflected back into the backlight, which is generally configured with high reflectivity to recirculate those rays back toward the prism optic (sometimes repeatedly), until they enter the prism optic at larger incident angle and are allowed to pass to the viewer of display. Rays incident at larger angles are at least in part refracted through the prisms, and on average over all angles, the average exit angles are smaller than the average entrance angles, when measured relative to the normal to the prism optic. The angle bending and recirculation process creates a narrower FWHM light distribution (approx. 70-95 degrees) when illuminated by approx. 120 degree Lambertian distribution, and also provides on-axis brightness enhancement, also called gain. Said another way, a planar 90-degree linear prism optic illuminated by a wide light distribution upon its flat surface and with appropriate recirculation will increase intensity at the nadir, while reducing the FWHM, and thus does not create a batwing distribution.
[0110]In contrast, it is known that if the light enters the prism side (rather than the smooth side) of a planar 90-degree linear prism film or optic, it will exit in two lobes, similar to a 1D batwing shape (as mentioned in U.S. Pat. No. 4,300,185 or U.S. Pat. No. 4,233,651). FIG. 3B illustrates how collimated light will be divided (refracted) into two branches by prism structures. The angular deviation of this refraction is determined by the refractive index of the material, and the sidewall angle of the prisms. Typical refractive indices for prism films are in the range of 1.45 to 1.6. Greater prism angle or greater refractive index will result in larger refraction angles. Even Lambertian light impinging onto the prism side of a prism film will exit that film in a split distribution, in which light is approximately a batwing shape. This use of a prism is referenced on the Fusion Optix website at http://fusionoptix.com/lighting/components/light-shapers.htm (as of May 17, 2013), a diagram adapted from which is shown in FIG. 3C. The reduction of light intensity at theta (θ)=0 degrees (straight down in the image) is called “nadir suppression.”
[0111]In some artificially-illuminated environments, linear luminaires are used, in suspended, surface-mount, or recessed configurations. Such luminaires usually involve multiple lighting fixtures arrayed in a line parallel to their long axes with or without extra space between the fixtures, or can comprise single continuous lighting fixtures with a long axis. We define the vertical plane parallel to the long axis of the luminaire as the phi=0 plane, and the vertical plane perpendicular to the long axis as the phi=90 degrees plane. In linear lighting, the continuous or quasi-continuous nature of the light emission in the phi=0 plane parallel to the long axes usually provides uniform illumination of a floor or flat surface along the phi=0 plane. As such, a batwing distribution may not be needed in the phi=0 plane. For linear fixtures, it may be desirable to have a batwing distribution in the phi=90 degrees plane to provide uniform illumination in the phi=90 plane on the flat surface. For linear fixtures, a batwing distribution in the phi=0 plane may be less useful than a batwing distribution in the phi=90 degrees plane.
[0112]Many 1D and 2D batwing distributions exist in the art.
[0113]Batwing distributions are known in the art, and are usually created using specific focusing optics (e.g. lenses and/or reflectors), and/or specific features in the geometry of a light source, such as lamp placement, and placement of internal or external baffles, louvers, openings, and placement of ordinary diffusers. Examples include US Patent Application Publication 20050201103 A1, US Patent Application Publication 20130044476 A1, U.S. Pat. No. 4,218,727 A, U.S. Pat. No. 5,105,345 A, U.S. Pat. No. 6,698,908 B2, U.S. Pat. No. 3,329,812, EP Publication 1925878 A1, U.S. Pat. No. 3,725,697, U.S. Pat. No. 7,273,299, U.S. Pat. No. 5,149,191, EP Publication 2112426 A2. In many cases the focusing optics, baffles, etc., increase the cost of a luminaire. These designs are generally strongly dependent on the placement of the light source, and generally require alignment of the reflectors, baffles, etc. with the light source. Designing these luminaires with 1D or 2D circular or rectangular batwing distributions is generally difficult and slow, requiring either advanced computer modeling or trial-and-error testing, which can be too costly for some smaller lighting manufacturers. In particular, rectangular and square batwing distributions are the most difficult to create, due to the lack of a radial symmetry.
[0114]In U.S. Pat. No. 3,721,818, Stahlhut describes an article capable of controlling light distributions, such as reducing glare and creating 1D and 2D batwing distributions. The article involves shaped surfaces on one or both sides of a planar substrate, with additional “light reducing areas” (e.g. paint) which can be opaque, reflective or absorbing. Undesirably, the need for these light reducing areas may both increase cost and decrease efficiency of the light fixture. In some embodiments, the need to create structures on both sides of the surface that are aligned to each other may also add expense and complexity.
[0115]In U.S. Pat. No. 3,866,036, Taltavull describes a planar substrate with prism-like structures including prisms or linear lenses with truncated tips upon which thick opaque structures are formed. These may create effective batwing light distributions but may be expensive and difficult to create, and the opaque structures may incur additional losses of light, reducing overall fixture efficiency. In addition, the lack of diffusion in these structures means that from certain viewing angles, the light source(s) may be visible as undesirable bright spots on the surface of the luminaire.
[0116]In U.S. Pat. No. 3,978,332, Taltavull describes a planar substrate with a ring-shaped structure including concentric prisms or linear lenses with truncated tips upon which are created opaque structures. These can create effective 2D batwing light distributions but may be expensive and difficult to create, and the opaque structures may incur additional losses of light, reducing overall fixture efficiency. Taltavull additionally uses the exact placement of lenses and a carefully designed reflector, all of which elements together combine to create the desired 2D batwing light distribution, which may add further expense.
[0117]In U.S. Pat. No. 4,161,015, Dey et. al., describe a luminaire with batwing distribution created by selective reflectivity from a multilayer interference filter with reflectivity and transmissivity that vary with angle of incidence. Unfortunately such an interference filter may be expensive to create, and may generally be wavelength-sensitive. In addition, when viewed from certain angles, there is undesirably no obscuring of the light sources.
[0118]In US Patent Application Publication 20090296401 A1 Gutierrez describes a system that uses a moving resonant mirror to create a desired light distribution, including batwing distribution. Such a system may suffer from excess power consumption, noise created by the mechanical motion, flicker, and possibly reliability issues associated with moving parts.
[0119]In U.S. Pat. No. 4,059,755 A, Brabson describes the use of three different prism optics in two layers to create a 1D batwing distribution. This system may undesirably need to be aligned to a linear source. Undesirably, the two layers of custom prism optics may be expensive, and may incur a reduction of efficiency associated with reflections from multiple optical interfaces.
[0120]In many other examples, including US Patent Application Publication 20090225543, US Patent Application Publication 20120275150, PCT Publication WO2012109141 A1, U.S. Pat. No. 7,658,513, US Patent Application Publication 20130042510, U.S. Pat. No. 8,339,716 B2, US Patent Application Publication 20130039090 A1, U.S. Pat. No. 7,273,299 B2, U.S. Pat. No. 7,731,395 B2, US Patent Application Publication 2009096685 A2, US Patent Application Publication 20110141734 A1, U.S. Pat. No. 7,942,559 B2, U.S. Pat. No. 7,993,036 B2, U.S. Pat. No. 6,568,822, individual light sources (typically LEDs or collections of LEDs) are modified using lenses, reflectors, light pipes, or the LED package, in close proximity to light sources. Many light distributions can be created this way (as known in the art), including 1D and 2D batwing distributions. In many general lighting applications, large numbers of LEDs (typically tens or hundreds) are used over the area of the luminaire, and the use of lensed LEDs with non-Lambertian distributions can be costly. Also, individual LEDs can be piercingly bright when unobscured, even if focused using localized lenses. To achieve desirable smooth appearance of a luminaire and obscure the light sources, additional diffusers may be required, incurring higher costs. Further, such diffusers may in some cases not be able to sufficiently homogenize the surface appearance of the luminaire without degrading the distribution created by the LEDs.
[0121]In U.S. Pat. No. 5,997,156 A, Perlo et. al. describe creating rectangular or square light distributions using rippled lenticular lenses or TIR prism lenses on planar substrates in conjunction with a collimated light source (in the example provided, using a parabolic reflector). However, the techniques mentioned may not work with Lambertian light sources.
[0122]In U.S. Pat. No. 5,243,506 A, a light-pipe architecture illuminated by a single source at the end of the light pipe uses prisms to couple light out of the light pipe at a point and in a direction substantially perpendicular to the surface of the light pipe at that point. By using metal masking in selective locations to determine where light can strike the prisms and escape the light pipe, 1D light distributions including 1D batwing distributions can be sculpted.
[0123]First-pass transmission is the fraction of incident light directly from the light source that is emitted through a diffuser in a luminaire. Light that is not emitted in the first pass may either be absorbed or reflected back into the luminaire. Such reflected light may be further absorbed or reflected by surfaces inside the luminaire, and some of such reflected light may thus have another chance to exit the diffuser on the second or later passes. High first-pass transmission may desirably result in high luminaire efficiency.
[0124]The use of prisms for retro-reflection is well known in the art. A prism film employing outward-facing prisms bent into a closed tube with an appropriate cross-sectional shape can serve as a light-pipe, accepting light that is transmitted into one or both ends of the tube, and guiding the light along the length of the tube using reflections from the prism film. In some light pipe designs, a scattering element is included inside the light pipe, specifically designed to scatter light out of the light pipe where it can provide useful illumination. Light Pipes are illuminated at one or both ends and do not contain a linear light source within the light pipe. Light Pipes have not been widely adopted, for a variety of reasons. Prism-based light pipes may leak a significant amount of light along their length, the leaked light often being leaked into all angles. Leaked light striking the light housing or ceiling may be partially absorbed leading to lower illumination on the desired illumination area. It can be difficult to efficiently couple light into a light pipe, as only certain numerical apertures or light ray angles may be guided. In many cases, higher numerical aperture light from the source may spill out near the source, with lower numerical aperture light being transmitted further, resulting in a light pipe that is undesirably brighter at the light-source ends than in the middle. This may also result in different brightness near the source versus in the middle when viewed from different viewing angles. Also because of the limited acceptance angles of light pipes, light sources may need to be somewhat collimated such as by using parabolic reflectors in order to efficiently couple light into the light pipe, disadvantageously adding cost and complexity. Light pipes are generally designed to have low first-pass transmission due to the need to convey light somewhat evenly across the luminaire's length, and may suffer undesirable low efficiency due to absorption internal to the light pipe or at its ends. Light pipes made from prisms may also be difficult to construct, as apparatus for forming and holding the prism film into the desired shape may be complex and may have to interact with the light pipe in some way, causing undesirable loss of light. Designs that include a light scattering element inside the light pipe may suffer from further difficulties in affixing the light scattering element in the desired location. Examples of light-pipe designs include U.S. Pat. No. 4,260,220, U.S. Pat. No. 4,542,449, U.S. Pat. No. 4,615,579, U.S. Pat. No. 4,750,798, U.S. Pat. No. 4,787,708, U.S. Pat. No. 4,791,540, U.S. Pat. No. 4,805,984, U.S. Pat. No. 4,834,495, U.S. Pat. No. 4,850,665, U.S. Pat. No. 4,906,070, U.S. Pat. No. 5,186,530, U.S. Pat. No. 5,309,544, U.S. Pat. No. 5,339,382, U.S. Pat. No. 5,475,785, U.S. Pat. No. 5,483,119, U.S. Pat. No. 5,715,347, U.S. Pat. No. 5,845,037, EP 0855044, U.S. Pat. No. 5,745,632, U.S. Pat. No. 7,658,514.
[0125]In U.S. Pat. No. 5,309,544 Saxe illuminates a prism-based light pipe from the side and employs a diffusely reflective light extractor along its interior to scatter light out of angles that will be guided by the light pipe toward a first side of the light pipe. The geometry of the surface is carefully planned such that the direction of travel of light reflected by the extractor will have a projection in the plane perpendicular to the optical axis that makes a fixed predetermined angle with the smooth interior surface of said first side. This requirement to maintain a constant input angle on the inner surface of the prism film is said to maximize efficiency of transmission through said first side. Light that is scattered to any of the other sides of the light pipe will be retroreflected, and must strike the sides and reflector one or more additional times before having another chance to be directed toward said first side. This may result in undesirable reduction of efficiency. The shape is not designed to produce a batwing light distribution, although in some cases it produces a “highly directed” beam of light, defined therein as a beam of light with a larger percentage of the light output in a small angular region. Saxe uses a substantially right-angle (90-degree) prism film.
[0126]In U.S. Pat. No. 6,863,420, Schutz describes and outward-facing prism film used to control glare. The light distribution produced is not a batwing, but may be substantially uniform over non-glaring angles, as illustrated by angles εg1 through εg2 in FIG. 11 of the '420 patent. The configuration of the '420 patent creates many reflected rays, as illustrated by label 14 in FIG. 11 of the '420 patent. Such reflected rays may result in low first-pass transmission and reduced efficiency of the luminaire.
[0127]In 20130063925, Boonekamp describes the use of a continuously-curved convex 90-degree prism for reduction of glare. The luminaire does not create a batwing distribution. Disadvantageously, the use of 90-degree prisms, a significant portion of which are oriented with bases perpendicular to the light source and hence having a high degree of retroreflection, may cause the luminaire to have low first-pass transmission and poor efficiency.
Additional References
[0128]In U.S. Pat. Nos. 7,660,039 and 7,837,361, Santoro et al. disclose diffusers that (a) reduce luminance at high viewing angles (known as glare), and/or (b) produce a 1D or 2D batwing luminous intensity distribution. Santoro uses non-prismatic microstructures, termed “kinoform diffusers,” that do not have retroreflection properties like prisms do. These kinoform diffusers have specific angle-bending properties for light rays such that when they are used in specific appropriate configurations, batwing distributions can be created from linear and/or point light sources. In some embodiments of the patents, non-planar and/or curved arrangements of diffusers produce batwing distributions. Kinoform diffusers are discussed in the '039 and '361 patents, and disadvantageously may require complex holographic methods of fabrication. Such methods may be expensive and difficult to control.
[0129]In the embodiments of FIG. 25A of the '039 patent and FIG. 25A of the '361 patent, an outwardly-folded diffuser is provided that creates a batwing distribution. The batwing distribution is in all planes, but is predominant in the phi=0 degree plane, parallel to the linear light source. Batwing distributions in the phi=0 plane may be less desirable than batwing distributions in the phi=90 degree plane for linear luminaires. The elongated surface structures of the kinoform diffuser are oriented perpendicular to the light source, and thus the “plane of diffusion” as defined in these patents is parallel to the light source. The embodiment does not use prisms.
[0130]In the embodiments of FIG. 27 of the '039 patent and FIG. 27 of the '361 patent, a diffuser comprising two curved sections is provided around a linear light source with opaque light shields on either side and creates a batwing light distribution. The batwing distribution is in all planes, but is predominant in the phi=0 degree plane, parallel to the linear light source. Batwing distributions in the phi=0 plane may be less desirable than batwing distributions in the phi=90 degree plane for linear luminaires. The elongated surface structures of the kinoform diffuser are on the inside surface of the diffuser facing the light source, and are oriented perpendicular to the light source, and thus the “plane of diffusion” is parallel to the light source. The embodiment does not use prisms.
[0131]In the embodiments of FIG. 29 of the '039 patent and FIG. 29 of the '361 patent, planar kinoform diffusers are added to either side of the curved diffuser embodiments of FIG. 27 of the '039 patent and FIG. 27 of the '361 patent, and the opaque light shields are removed. The elongated surface structures of the added planar kinoform diffusers are on the outside surface of the diffuser facing away from the light source, and are oriented parallel to the light source, and thus the “plane of diffusion” is perpendicular to the light source. The planar side diffusers may add additional light in a batwing distribution in the phi=90 degree plane perpendicular to the light source. This embodiment disadvantageously uses kinoform diffusers and requires placing them at two different orientations which prevents the use of a single shaped diffuser and may add cost. The embodiment does not use prisms.
[0132]In the embodiments of FIG. 32 of the '039 patent and FIG. 32 of the '361 patent, a curved kinoform diffuser positioned below a linear light source, and planar kinoform diffusers are placed on either side of said curved diffuser. A batwing distribution in the phi=90 degree plane perpendicular to the light source is formed. The elongated surface structures of the kinoform diffuser are on the outside surface of the diffuser facing away from the light source, and are oriented parallel to the light source, and thus the “plane of diffusion” is perpendicular to the light source. Further teachings about this embodiment in the '361 patent including FIGS. 32-1 through 32-4 show that the central curved region does not contribute to the batwing distribution, but rather has a Lambertian-like distribution similar to the light source, the batwing distribution being generated substantially by the planar kinoform diffusers on the sides. The embodiment does not use prisms.
[0133]In the embodiments of FIGS. 32-5, 32-6A, and 32-6B of the '361 patent, the embodiments of FIG. 32 of the '039 patent and FIG. 32 of the '361 patent are modified, replacing the curved center section with a central planar diffuser that may be offset from the planes of the side diffusers. The central planar diffuser does not create a batwing distribution and may be of a type other than a kinoform diffuser, including a sandblasted diffuser or perforated metal. A batwing distribution in the phi=90 degree plane perpendicular to the light source is formed, the batwing distribution being generated substantially by the planar kinoform diffusers on the sides. The embodiment does not use prisms.
[0134]In the '039 patent, the diffuser may need to include multiple light scattering elements, “on each of which are one or more sub-elements.” In practice these sub-elements may be very difficult to create and control. Advantageously, various embodiments described herein do not require kinoform diffusers and do not require such sub-elements. Advantageously, various embodiments described herein employ prism films that are widely and inexpensively available.
[0135]In U.S. Pat. No. 8,047,673, Santoro describes a light control device implemented with multiple planar diffusers. The light control devices and luminaires disclosed create 1D batwing light distributions by means of a central lamp, multiple diffusers, and openings with carefully designed placement. These patents do not use a non-planar prism optic with prisms facing away from the light source. The individual diffusers of the luminaire do not create batwing distributions. Rather the distribution is created using the diffusers, lamp, openings, and internal reflections working collectively, and thus is distinct from various embodiments described herein, which can create 1D batwing distributions from non-planar shaped outward-facing prism elements.
[0136]In U.S. Pat. No. 6,612,723, Futhey et. al. create substantially collimated distributions, using linear light sources and inward-facing prisms formed in various shapes to direct light in a direction substantially perpendicular to the luminaire. They do not create batwing light distributions.
[0137]In U.S. Pat. No. 7,537,374 and U.S. Pat. No. 7,815,355, backlights are described in which a curved transflective (partially transmissive and reflective) optic is formed in a shallow curve to more uniformly illuminate the backlight. In some embodiments, prism films may be used for the curved transflective optic, but in those cases the prism film is said to be preferably inward-facing. The patent not produce a batwing light distribution pattern.
[0138]In U.S. Pat. Nos. 7,261,435 and 7,229,192, Mayfield et. al. disclose a luminaire that uses a curved lens containing linear shapes, in either inward-facing or outward-facing orientations to optically reduce the surface brightness of the light source, provide diffused non-batwing illumination, and reduce light at high angles (glare). Most preferred embodiments use rounded lenses rather than triangular prisms with a short focal length intended to provide even diffusion. The lenses do not produce a batwing distribution.
[0139]In U.S. Pat. No. 6,280,052, White describes a curved optic consisting inward-facing prisms arranged in a pointed shape that has two symmetric halves both of which are convex facing toward the lamp. The luminaire produces a distribution that is approximately uniform over all angles, and thus is not a batwing light distribution.
[0140]CN 202532218 U discloses a lamp structure with batwing light intensity distribution. The lamp structure comprises at least two light-emitting diode (LED) groups, a light guide plate, a reflecting part and a prism sheet, and is characterized in that: the light guide plate is provided with a first surface and a second surface; and the first surface is provided with a micro structure. Distribution in a way that both sides are sparse while middle is dense is adopted, so that the refraction angle of light rays is changed, and the light rays are refracted out of the light guide plate. Light rays are uniformly scattered effectively through the geometric structure on the prism sheet facing the light guide plate, so that batwing light intensity distribution is achieved.
Potential Advantages
[0141]Various embodiments described herein can create useful light distributions including a 1D linear batwing light distribution using a prism optic with[0142]Prisms oriented substantially parallel to linear light source[0143]Prisms outward-facing, i.e. on the surface facing away from the light source[0144]Prisms formed into an extended non-planar shape with cross section in the plane perpendicular to the light source.
[0145]Various embodiments described herein can contain at least one section of continuously-curved outward-facing prism.
[0146]Various embodiments described herein can create batwing light distributions using inexpensive commercially-available prism films.
[0147]Various embodiments described herein can create narrow or collimated light distributions.
[0148]Various embodiments described herein can have the prism film shape chosen such that few or substantially none of the prisms are oriented such that their bases are perpendicular to light rays emitted by the light source into said prisms.
[0149]Various embodiments described herein can create useful light distributions including a 1D linear batwing light distribution using a prism optic with a substantially linear light source, the prisms oriented substantially parallel to the long axis of the light source.
[0150]Various embodiments described herein can create useful light distributions including a 1D linear batwing light distribution using a prism optic with two or more substantially parallel substantially linear light sources, the prisms oriented substantially parallel to the long axis of the light source.
[0151]Various embodiments described herein can provide a contiguous or monolithic prism optic that can create useful light distributions including a 1D linear batwing light distribution.
[0152]Various embodiments described herein can provide a prism optic with high optical transmission, having substantially no light-absorbing materials.
[0153]Various embodiments described herein can provide a prism optic with high optical transmission, having prism orientations chosen to minimize retro-reflection of light back into the interior of the luminaire.
[0154]Various embodiments described herein can provide a prism optic that obscures or helps obscure light sources, including but not limited to LEDs and fluorescent lamps.
[0155]Various embodiments described herein can provide a prism optic than can be efficiently and inexpensively mass-produced in areas large enough to be suitable for use in general lighting.
[0156]Various embodiments described herein can provide a prism optic that reduces luminance at high viewing angles relative to a linear source.
[0157]Various embodiments described herein can provide a prism optic that creates a one-sided distribution suitable for applications including wall-wash and/or cove lighting.
[0158]Various embodiments described herein can provide a prism optic which creates desired light distributions including batwing distributions and one-sided distributions when used with appropriately configured specular or diffuse reflectors.
[0159]Various embodiments described herein can provide a luminaire employing a prism optic, the luminaire emitting light into a batwing distribution.
[0160]Various embodiments described herein can provide a luminaire employing a prism optic, the luminaire emitting light into a one-sided distribution suitable for applications such as wall-wash and/or cove lighting applications.
[0161]Various embodiments described herein can provide a luminaire employing multiple light sources and prism optics, the light sources and prism optics cooperating to provide a batwing light distribution.
[0162]Various embodiments described herein can provide a luminaire with a distinct visual appearance that may be pleasing to a viewer.
Measurement
[0163]Light distributions are typically measured using goniometric apparatus similar to that described in the IES LM-79 standard, as illustrated in FIG. 4. In FIG. 4, a luminaire or illuminated optical device is depicted (labeled SSL product) emitting light in a downward dimension. The two circles with dots on their perimeters represent planes at two different azimuthal angles φ (phi). In each of these planes, the polar angle θ (theta, ranging from −180 to 180 degrees) is defined as indicated. Example measurement points in the phi=0 degree and phi=90 degree planes are depicted as dots. At each of these points, luminous intensity is measured as a function of the theta angle from the principle axis of the light source. This luminous intensity is measure by an optical detector, the optical detector and/or light source moved relative to each other so that the optical detector measures light at the desired angles. In practice a light distribution can be measured at any group of phi and theta points desired. Many lights emit substantially in one hemisphere, and thus theta will often be measured from −90 to 90 degrees.
General Description
[0164]Various embodiments described herein can provide a prism optic comprising a substrate having a first and second surface, the first surface having pattern elements comprising a plurality of substantially parallel, linear prismatic structures, or prisms, said substrate shaped into a non-planar shape such that the prisms are parallel to one or more linear light sources.
[0165]In many embodiments, the prisms are substantially isosceles triangular in cross-section, and may include other f